In a medium sized bowl, whisk all-purpose flour, cornstarch, baking powder and salt. Set aside.
Using a stand mixer fitted with the paddle attachment or in a large bowl using a handheld electric mixer, beat unsalted butter, granulated sugar and brown sugar on med-high speed until well blended.
Add ube jam and ube extract and continue beating until incorporated.
Add eggs and beat until combined.
Add your flour mixture to your ube mixture in thirds and beat until no more streaks of flour remain. Remember to scrape the bottom and sides of your bowl in every step.
Stir in white chocolate chips, cover the bowl with plastic wrap, and chill the batter for at least 3 hours.
When ready, preheat your oven to 350F and line a baking sheet with parchment paper.
Scoop about 2 tablespoons of dough and roll into balls using your hands. Place on cookie sheet with about 2 inches of space around each cookie.
Bake for 10-11 minutes or until the cookies are just set.
Remove from oven and allow to cool completely on the pan. Optional but highly recommended step: as soon as you remove your cookies from the oven, gently press a few pieces of white chocolate chips on top of each cookie. This makes them prettier but note that this adds to their sweetness as well.
The total number of cookies will depend on how big or small you roll your cookie dough.
Not all ube jams are made the same. I make my own ube halaya and if you use that to make your ube cookies, you don’t need to change anything in the recipe. If you use store-bought ube jam, taste your cookie dough before adding in the egg so you can decide if you need more sugar, ube or both. Make sure to add sugar or ube in small increments.
See post for complete step-by-step photos, lots of baking tips, and FAQs.